1. Field of the Invention
The present invention relates generally to prosthetic feet. More particularly, the present invention relates to prosthetic feet with an energy transfer medium including a variable viscosity fluid.
2. Related Art
Many individuals have lost a limb for various reasons including war, accident, or disease. In most instances, these individuals are not only able to live relatively normal lives, but physically active lives as well. Often times, these individuals are aided in their everyday lives by a prosthetic limb. The objective of prosthesis is to provide an artificial limb that simulates the function and natural feel of the replaced limb.
With respect to prosthetic feet, the development of a functional and natural artificial foot has been limited only by material and imagination. Many designs have attempted to copy the anatomy of the foot or simulate its actions by replacing the bones and muscle with various mechanical components. Other designs have departed radically from mere anatomical copying or mechanical simulation by replacing the entire foot with an energy storage element, such as a spring. As the user steps onto the foot, the user""s weight compresses the spring. As the user moves forward, the user""s weight comes off the foot and the energy stored in the spring is used to propel the user forward. Examples of such energy storing, spring-like feet include U.S. Pat. Nos. 5,037,444; 4,547,913; 5,181,932 and 5,976,191.
The prosthetic feet typically include spring-like members that are typically flexible and resilient. In order to provide a natural feel and cushion of a natural foot, the members must be flexible and deflect under the user""s weight. Such flexibility and the ability to deflect often require the members forming the foot to be structurally weak, or more flexible. On the other hand, it is desirable to make the members as strong or stiff as possible from a structural and durability standpoint. Thus, there may be a trade-off between obtaining a sufficient cushion or feel, with members that are weak or flexible and over-deflect, and obtaining a solid and durable structural foot, with stiffer members.
The stiffness of prosthetic feet typically varies according to the intended use. Feet intended for everyday use typically require a soft feel, and thus incorporate a softer spring. Feet intended for athletic use typically require strength, and thus incorporate a stiff spring. Feet designed for particular purposes are typically unsuited for other purposes. Stiff, athletic feet are too hard for everyday use, and soft, everyday feet are too fragile for athletic use. Multiple-use feet have been designed which are capable of many different uses, but without being particularly well suited for any specialized use.
In addition, users may have different weights. Thus, prosthetic feet may require a high degree of custom design, or be particularly tailored to the individual user. However, it is desirable from a cost and manufacturing standpoint to create a foot that is usable by many sizes of individuals.
It has been recognized that it would be advantageous to develop a prosthetic foot with adjustable stiffness for accommodating different uses or different users.
The invention provides a prosthetic foot device with variable stiffness response with a variable energy transfer medium disposed between first and second members. The first member can be coupled to an amputee, while the second member can be coupled to the first member, and can operate between the first member and ground during use. The variable energy transfer medium transfers at least some energy from the second member to the first member during use. The energy transfer medium advantageously includes a variable viscosity fluid such that the variable viscosity fluid, and thus the energy transfer medium, variably transfers energy between the first and second members to vary stiffness of the prosthetic foot device.
In accordance with a more detailed aspect of the present invention, the first and/or second members can include a resilient member capable of storing energy during deflection.
In accordance with another more detailed aspect of the present invention, the variable viscosity fluid can include a shear stiffening material that increases in viscosity as a load or strain, or load rate or strain rate, applied to the shear stiffening material by the second member increases.
In accordance with another more detailed aspect of the present invention, the variable viscosity fluid can include a magneto or electro rheologic fluid responsive to a magnetic or electric field. A transducer can be coupled to the first and/or second member to sense a load factor in the member or foot device. A power source and control electronics can be coupled to the transducer and the variable viscosity fluid to apply the magnetic or electric field in response to the load factor sensed by the transducer.
In accordance with another more detailed aspect of the present invention, the first member can include an upper member having an attachment section to be coupled to a socket, and extending downwardly therefrom. The second member can include a lower foot member having a heel section disposed at a natural location of a heel of a user, and a toe section disposed at a natural location of a toe of the user.
In accordance with another more detailed aspect of the present invention, the first member can include an upper forefoot member having an attachment section to be coupled to a socket, and extending downwardly therefrom. The second member can include a lower heel member having a heel section disposed at a natural location of a heel of a user, and an attachment section attached to the upper forefoot member.
In accordance with another more detailed aspect of the present invention, the first member can include both 1) an upper forefoot member having an attachment section to be coupled to a socket, and extending downwardly therefrom, and 2) a lower heel member having a heel section disposed at a natural location of a heel of a user, and an attachment section attached to the upper forefoot member. The second member can include a forefoot reinforcement member and/or a heel reinforcement member. The forefoot reinforcement member can be disposed above the upper forefoot member, while the heel reinforcement member can be disposed above the lower heel member.
In accordance with another more detailed aspect of the present invention, the first member can be an adaptor, while the second member can be a prosthetic foot. The second member can include at least an upper member having an attachment section attached to the adaptor and configured to be coupled to the socket by the adaptor, and extending downwardly therefrom.
Additional features and advantages of the invention will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the invention.